Retarder including a porous wall fluid restricting means



April 2, 1968 D. T. CHAPUT ETA RETARDER INCLUDING A POROUS 3,375,908 L FLUID ESTRICTING MEANS Filed Dec. 13, 1965 F l G. 2

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INVENTORS DALE T. CHAPUT BY ROBERT A. HASKELL I g A"rTORNEY$ United States Patent C) 3,375,908 RETARDER INCLUDING A POROUS WALL FLUID RESTRICTING MEANS Dale T. Chaput, Monterey Park, and Robert A. Haskell,

Long Beach, Calif., assignors to Aerojet-General Corporation, El Monte, Calif., a corporation of Ohio Filed Dec. 13, 1965, Ser. No. 513,288 9 Claims. (Cl. 188-94) ABSTRACT OF THE DISCLOSURE This disclosure concerns a mechanism for retarding the movement of a member so as to delay the completion of such movement, wherein the movement-retarding medium comprises a wall made of a porous material permeable to fluid. The porous wall cooperates with a flexible fluid impervious diaphragm so as to form a closure for one end thereof to define a chamber of variable volume therewith. A piston is disposed at the other end of the diaphragm and is connected thereto in a fluid-tight relations-hip. Upon moving the piston in a direction either toward or away from the porous wall, the volume of the chamber changes as fluid is transferred through the porous wall. The degree of porosity of the porous wall restricts the rate at which fluid transfer therethrough may occur and thereby controls the rate of movement of the piston. Thus, the restricted rate at which fluid transfer through the porous wall may occur serves to retard movement of the piston so as to delay completion of such movement. Fluid transfer through the porous wall may occur from the chamber outwardly to a fluid reservoir on the opposite side of the porous wall when the piston is advanced in a direction toward the porous wall. Alternatively, the fluid transfer through the porous wall may occur from the fluid reservoir into the chamber when the piston is retracted in a direction away from the porous wall. One application of the delay mechanism is in the detonation of an explosive charge, where the delay mechanism serves to provide a controlled delay in the movement of an actuator member to an explosivedetonating position.

The present invention relates generally to mechanical delay devices, and, more particularly, to such devices utilizing the metering of. a fluid through a porous medium as a delay means.

In many cases it is important that a delay device should be small, light in weight and capable of accurate functioning under wide variations of ambient temperature and pressure.

Various delay devices are known that depend upon the metering of a fluid through a small orifice to provide a delayed action, but such devices are relatively complicated and expensive to produce.

It is therefore an object of the invention to provide a mechanical delay device that is of light weight, simple construction and inexpensive to produce.

It is a further object of the invention to provide a delay device capable of functioning accurately over a wide range of ambient temperature and pressure.

Further objects and features of the invention will hereinafter appear from the following description and accompanying illustrative drawings in which the device is described as operated by air pressure, but it is to be understood that the device is not necessarily restricted to the use of this fluid alone.

The above described objects are achieved by a device having a plunger slidable within a similarly dimensioned housing having one end closed by a porous wall. A draphragm comprising a bag-shaped member of flexible fluldice impervious material is arranged in the space between the Inner end of the plunger and the porous wall and attached to the end of the plunger. Movement of the plunger is slowed by the pressure-time effect of a fluid moving through the porous wall.

In the drawings:

FIG. 1 is a longitudinal sectional view of the delay device of the invention, the parts being shown in the initial position for a first mode of operation, or in final position for a second mode;

FIG. 2 is a view similar to FIG. 1, but with the parts in intermediate disposition thereof; and

FIG. 3 is a view similar to FIG. 1, but with parts arranged in initial position for the second mode of operation, or in final position for first mode operation.

With reference particularly to FIG. 1, there is shown generally at 10 one form of the invention for providing mechanical delay to a movement in a right-to-left direction. As illustrated, the device is in the relaxed or nonactuated condition.

There is provided a substantially cylindrical housing 11 and a piston or plunger 12 slidably received within. The forward or leading end 13 of the piston is of reduced diameter providing a space between the outer surface of the leading end and the inner surface of the housing for a purpose that will be more fully brought out later. A flexible baglike member or diaphragm 14 is secured to the terminus of the leading end 13 by a threaded retaining means 15. The baglike member has a thickened edge or rim 16 that is received within a similarly dimensioned shoulder 17 of the housing. A porous wall 18 is fittingly received within the open end of the housing and in hearing contact with the edge or rim of the baglike member. A fluid reservoir 19 in open communication with the outer surface of the wall 18 is aflixed over the end of the housing 11 *by threaded members 20 serving to compressingly confine the rim 16 against the shoulder 17 and provide a fluid sealed space or chamber 21, within the member 14 except for the porous wall.

The porous wall 18 is contemplated as constructed of a material having natural openings of microscopic or submicroscopic size. That is, for example, the porous condition obtained with certain sintered metals provides an excellent means for this purpose.

As to the material composing the flexible member 14, a number of rubber based materials can be utilized for this purpose. To date, however, relatively thin siliconrubber sheeting has been found to possess the best overall combination of flexibility and fluid sealing properties.

In operation, the actuation movement is applied directly to the piston 12 to move it in a right-to-left direction (by a means not shown). This movement is transmitted to the member 14 and serves to compress a fluid (air, for example) contained within the space 21, see FIG. 2. The compressed fluid acts as a retarding influence on the movement of the piston and provides the desired mechanical delay. Increase of the pressure in the space 21 is dissipated through leakage of the fluid via the porous wall to the reservoir 19. Although the final mechanical disposition of the piston can vary, it is assumed here for purposes of presentation that it is when the retaining means 15 is in contact with the porous wall.

It will be noted that in the intermediate stages of opera-tion (FIGS. 2 and 3) the baglike member 14 is folded around the reduced diameter end 13 of the piston. It is to accommodate this material that the piston is provided with a reduced diameter, otherwise rupture of the member and release of the pressurized fluid might result.

The described device can also be used to delay move ment of the piston in the other direction, that is, from left-to-right as shown in the drawings. With the device set up as in FIG. 3, there exists a fluid pressure equilibrium condition in the space 21. A supply of the fluid to be used is provided in the reservoir 19. Movement is applied to the piston 12 such as to withdraw the piston from the housing. At an intermediate position as in FIG. 2, a reduced pressure condition is created in the space 21 serving to retard movement of the piston and provide the delay. The final position in this case is that of FIG. 1. Due to the lowered pressure of the space 21, the relatively pressurized fluid in the reservoir 19 moves through the porous wall into the space 21, eventually producing a pressure equilibrium condition.

Although the above description has based operation upon air as the fluid medium for producing delay, it is considered to be within the spirit of the invention to utilize any fluid, either gas or liquid. The exact choice of fluid will depend upon such factors as length of delay desired, temperature and pressure environment and degree of porosity of the wall 18.

In the practice of the invention there is provided a device for supplying a time lag or delay in the physical movement of a member after initiation of the movement. Although there are many possible uses for such a device, one use for which the invention would be ideal is in delaying the actuator arm or member of an explosive charge detonation means.

Moreover, when the device incorporates a member 14 constructed of relatively thin silicone rubber, uniform operation is obtainable over a wide range of ambient temperature and pressure conditions.

Preferred embodiments of the invention have been described and shown in the accompanying drawings as illustrative, but not as limitative of the invention, since changes in the described embodiments may be made by those skilled in the art without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

'1. In combination,

a flexible fluid impervious container having an open end,

a wall in juxtaposition to said container and closing the open end thereof to define a chamber of variable volume therewith, said wall being made of a porous material permeable to fluid,

a member disposed on the end of said container opposite from said porous wall,

the volume of said chamber being varied in response to relative movement between said member and said porous wall changing the distance therebetween for effecting transfer of fluid through the porous wall, and

the degree of porosity of the porous wall restricting the rate at which fluid transfer may occur therethrough so as to control the rate of relative movement between said member and said porous wall,

whereby the restricted rate at which fluid transfer may occur through the porous wall serves to delay completion of the relative movement between said member and said porous wall by retarding the rate of such relative movement.

2. An apparatus as set forth in claim 1, in which the porous wall is constructed of sintered metal.

3. In combination,

an elongated housing,

a piston received within said housing and axially movable therein,

a flexible fluid impervious diaphragm disposed within said housing forwardly of said piston, said diaphragm including an axially extending annular portion terminating in an open end remote from said piston and engaging said housing in sealing relation therewith,

a wall in juxtaposition to said diaphragm and closing the open end thereof to define a chamber of variable volume therewith, said wall being made of a porous material permeable to fluid,

said chamber containing fluid therein,

the volume of said chamber being decreased in response to forward axial movement of said piston toward said porous wall to pressurize the fluid within said chamber, and

the degree of porosity of the porous wall restricting the rate at which fluid may be transmitted from the chamber through the porous wall so as to control the rate of forward axial movement of said piston, whereby the pressurized fluid contained in said chamber acts as a temporary retarding force delaying completion of the forward axial movement of said piston until sufiicient fluid is transmitted from said chamber through said porous wall. 4. An apparatus as set forth in claim 3 further including a fluid reservoir connected to said porous wall on the side thereof opposite from said diaphragm, and said porous wall having one major wall surface facing the interior of said fluid reservoir and its other major wall surface expose-d to the fluid in said chamber, whereby fluid being transmitted from said chamber through said porous wall is directed into said reservo1r. 5. An apparatus as set forth in claim 4, wherein the forwardly disposed end portion of said piston is of reduced diameter to define an axially extending annular space between said housing and the forwardly disposed end portion of said piston, and the axially extending portion of said diaphragm folding back onto the forwardly disposed end portion of said piston to lie within the axially extending annular space in response to forward axial movement of said piston. 6. An apparatus as set forth in claim 4, wherein said diaphragm includes an annular radially inwardly extending rear end portion and a radially outwardly extending annular rim of increased thickness at the forward end portion of said axially extending portion thereof bounding the open end of said diaphragm, said housing being provided with an annular internal radial shoulder disposed at the forward end thereof,

said porous wall abutting said annular thickened rim of said diaphragm and holding said annular thickened rim against said internal radial shoulder of said housing in seated relation therewith, and

means connecting the annular radially inwardly extending rear end portion of said diaphragm to the forward end of said piston.

7. An apparatus as set forth in claim 6, wherein said means connecting the annular radially inwardly extending rear end portion of said diaphragm to the forward end of said piston comprises a tubular internally threaded fitting secured to the forward end of said piston and having an annular radially outwardly extending collar thereon, and

a stud having an enlarged head and being threadably received by said fitting with the enlarged head of said stud and the collar on said fitting being disposed in opposed relationship;

the annular radially inwardly extending rear end portion of said diaphragm being clamped vbetween the opposed enlarged head of said stud and the collar on said fitting so as to be secured to the forward end of said piston in fluid-tight relation, and

the enlarged head of said stud engaging said porous wall upon completion of the forward axial movement of said piston.

8. An apparatus as set forth in claim 4, in which the porous wall is constructed of sintered metal.

9. In combination,

a flexible fluid impervious container having an open end,

a wall in juxtaposition to said container and closing the open end thereof to define a chamber of variable volume therewith, said wall being made of a porous material permeable to fluid,

said chamber being in substantially fluid-free condition,

a reservoir of fluid connected to said porous wall on the side thereof opposite from said container so that said porous wall has one major wall surface exposed to the fluid in said reservoir and its other major Wall surface facing the interior of said chamber,

a member disposed on the end of said container opposite from said porous wall,

means connecting said member and said container,

the volume of said chamber being enlarged in response to movement of said member in a direction away from said porous wall to reduce the pressure within said chamber, and

the degree of porosity of the porous wall restricting the rate at which fluid from said reservoir may .be transmitted through the porous wall into said chamber so as to control the rate of movement of said member away from said porous wall,

whereby the reduced pressure within said chamber acts as a temporary retarding force delaying completion of the movement of said member away from said porous wall until sufficient fluid is transmitted from said reservoir through the porous wall into said chamber.

References Cited UNITED STATES PATENTS 1,085,818 2/1914 Oxnard 7418.2 X 2,068,948 1/1937 Freeman 188-94 X 2,853,159 9/1958 Kuhn 18894 2,938,704 5/1960 Quail 251368 X 2,946,554 7/1960 Asker et a1. 251-368 X 3,302,756 2/1967 McIntyre 188-38 MILTON BUCHLER, Primary Examiner, G. E. HALVOSA, Assistant Examiner. 

